In one aspect, the present invention relates to a method for packaging compressible fluids in predetermined quantities in tubular cartridges or the like. In another aspect, this invention relates to an apparatus for use with a cartridge loading mechanism which loads compressible, gas containing, gel compositions into cartridges and provides for accurate metering of such gel compositions into the cartridge packages. In still another aspect, this invention relates to the packaging of gelled explosive compositions, which are compressible in nature because of entrapped air or other gases, and which are packaged in tubular cartridges filled with filling tubes to which a predetermined amount of gel explosive composition is delivered via a piston feed apparatus.
Handling and packaging of viscous liquid compositions which are compressible because of the presence of entrapped gases therein presents problems which are unique because of the physical characteristics of the material. When gelled fluid materials containing entrapped gases are packaged in individual containers for use by consumers, it is conventional to deliver such fluids to the packages via elongated conduit filler tubes through which the gelled fluid is forced under pressure. One means for delivering such gelled fluids to containers in predetermined, closely metered, quantities is to use a piston cylinder arrangement. In such a filling apparatus a cylinder is first allowed to communicate with a reservoir of the gel fluid material, the piston is withdrawn within the cylinder so as to create a suction and thereby fill the cylinder with the gel fluid, the cylinder then is disconnected from the reservoir of gel fluid and the outlet of the cylinder is directed to filler tubes and the piston plunged downward through the cylinder thereby delivering a predetermined quantity of gel-type fluid out of the cylinder, through the filler tubes and into the packages which can comprises, for example, cardboard, paper or plastic cartridges.
In the packaging of gel-type explosive compositions which have been sensitized by incorporating therein occluded air or other gases, delivery of the explosive compositions to paper cartridges via a filler system such as that described above presents unique problems because of the high compressibility of the gel explosive compositions. This high compressibility is a direct result of the fact that the gel explosive compositions are sensitized (so as to be more easily detonable) by admixing therewith air, or other gases, and entrapping the gases within the gel by providing enough guar gum or the like so that the occluded gases will stay dispersed within the gel explosive composition and will not coalesce and separate out of the explosive composition. A consequence of the high compressibility of such gel explosive compositions is that when they are packaged the presence of occluded gases causes the explosive gels to become highly compressed when pumped through the filler tube and into the cartridges via a pressure source such as the filler piston-cylinder arrangement described above. The residual portion of explosive composition which is left behind in the filler tube, after the predetermined amount has been delivered to the cartridge packages is, of course, desirable so that when the next cartridge is filled a steady stream of explosive composition will be delivered thereto with no air pockets separating the residual explosive composition in the filler tube from the delivered to the filler tube from the pressurized delivery source. In the past, however, the compressibility of the gel explosive compositions has caused problems in that once the pressure from the pressurized filler source is relieved, and the filler tube removed from the cartridge being filled, the remaining portion of the explosive gel contained within the filler tube will no longer be subjected to pressures sufficient to keep it in a compressed state. Thus, the explosive composition contained within the filler tube will tend to expand, causing the gel explosive composition to leak or dribble from the open end of the filler tube. Such loss of explosive gel compositions is both expensive and hazardous and is, therefore, very undesirable. Furthermore, when the gel explosive compositions are being packaged in cardboard cartridges or the like, excess explosive gel materials dripping from the filler tube is undesirable in that it will contaminate the outside of such cartridges and washing such excess off with water may cause some damage to the containers.
Another problem associated with the packaging of explosive gel compositions is blockage and/or valve damage which may occur if solid lumps of material are present in the composition being delivered under pressure through filler tubes to packaging containers. For example, undissolved lumps of guar gum, conventionally used to thicken gel explosive compositions, may cause blockage or damage at constricting valve sites within the loading apparatus.
Thus, it is desirable to have a method and apparatus for loading compressible gel type fluids containing entrapped gases into containers therefor in predetermined quantities wherein the problems caused by the expansion of such fluids between filling cycles, and the presence of solid particles in the composition, are alleviated.